Dear friends and followers, Welcome back to my channel.
Today, we'll be taking a closer look at why the pilots of this plane dumping fuel,
and what that's got to do with a plastic water bottle. So let's started.
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In this video here, it's pretty obvious that something is off with this plane.
Why is there white spray coming out of the rear of the wings?
This plane is currently performing the jettison procedure or better known as fuel dumping.
Your imminent reaction probably is "what a waste and pollution of the environment"
"Why would pilots dump costly fuel overboard, which you as a passenger has just paid for?"
Did the pilots miscalculate the fuel they need from the trip to A to B?
And before we can answer those questions, we have to look at some weight limitations of airplanes.
So, for today's video, we'll be using a Boeing 747, and in a minute, you'll see why.
So, imagine you and your crew are sitting in a 747
preparing for a flight from Munich to Los Angeles.
So, the airplane's current weight is the so-called dry operating weight (DOW).
Then the payload comes on board - this is the passengers and the cargo -
and then you have the so-called zero fuel weight.
Then, the fuel truck connects to the wing and fuels the plane with a calculated fuel to reach your destination - the so called trip fuel -
plus contingency, plus alternate, final reserve, and taxi fuel, or better known as the block fuel.
If you add up all weights, you have here today's takeoff weight.
But for today's video, the landing weight plays a more important role.
So, the Boeing 747's maximum landing weight is three hundred and twelve thousand kilos,
which is a structural weight limit.
Now, you might ask,
"How can the maximum structural landing weight be lower than the takeoff weight if the plane is already so heavy upon takeoff?"
Now, all other limiting weights aren't as much subject to impact forces
as compared to the landing weight, and therefore, it is much lower.
Meaning, engineers have done the math and decided that if the pilots land the plane with the descent rate
of not more than roughly 300 to 400 feet per minute, at a maximum landing weight of 312,000 kilograms,
the plane won't suffer any structural damages primarily in the landing gear and airframe structure.
And any landing weight above the maximum will have the consequence that the plane most probably will have suffered internal damage
and Its structural integrity will be impaired after a so-called "overweight landing."
And this is where the plastic water bottle comes to play.
Now, with a little imagination,
you here can see our 747 shortly before landing at Los Angeles.
So, this water bottle shows the remaining fuel, the passengers and cargo,
and the crew plus the actual weight of the plane,
minus the burnt trip fuel, and you can see the landing weight is well below the maximum landing weight.
So let's drop the bottle out of a height relative to the plane's weight and vertical speed upon touchdown.
As you can see, no damage.
Now, let's say we're just crossing the Atlantic and your senior cabin crew member comes into the cockpit,
stating that one of her passengers just had a heart attack.
Now the flight attendants and an onboard doctor are doing their best to help the passenger,
but decide that the passenger immediately needs to get to a hospital.
The nearest suitable airport is Dublin. You quickly check your current airplane weight and realize
you're highly overweight for an immediate landing.
So, back to our imaginary plane.
The same airplane, same passengers and luggage, and crew, but loads of yet unburned fuel,
increasing your current landing weight, which is obviously way above the maximum limit.
Meaning, if you now try to immediately on the plane, this could potentially happen:
Your plane could suffer severe structural damages resulting in months of repairs,
or even irreparable damages, leading to a total hull loss.
Also keep in mind, a higher weight results in a higher landing speed,
increasing the stop margin, creating a potential runway overrun, so what do you do?
This is where the fuel jettison procedure comes to play.
To quickly reduce the airplane's weight, the pilots opened a spring-loaded valves via the fuel dumping panel,
and then now, unnecessary fuel gets literally dumped overboard.
It leaves the aircraft through a specific hose on each wing,
usually closer to the wing tip and further away from the engines.
So, why did I specifically say "spring loaded"?
Now, the valves open electrically and are hold in the open position,
but in case there's electrical failure during that dumping procedure,
the spring pushes the valve back into its closed position.
The dumping rate on the 747 is approximately two tonnes per minute,
plus the fuel burn during the procedure.
So, let's do the math how long we would have to open the valve until reaching an appropriate landing weight.
Okay, you guys, quickly to the drawing board. This is the current weight the airplane has right now.
This is the maximum landing weight.
And then you subtract that from that, and you get the weight you have to lose,
so those are the 77 tonnes we have to lose in order to not be above the max landing weight in Dublin.
So, as previously mentioned, the fuel dumping rate of the Boeing 747 is 2 tonnes per minute,
but you also have to add the fuel burned during that time and the 747 burns 12 tonnes per hour,
so you have to calculate how much it uses per minute and then add that to the fuel dumping rate.
Okay, here we have the calculation: 12 tonnes equals 60 minutes,
1 minute equals how many tonnes?
So you've got the 12 tonnes right here, times 1 minute, divided by 60 minutes,
Crosses out the minutes, gives you 0.2. tonnes per minute,
which you have to add onto the fuel dumping rate of 2 tonnes (per minute).
Okay, so here we have the final calculation. We have 77 tonnes divided by 2.2 tonnes per minute and that equals
35 minutes for the fuel dumping procedure.
And right at the point where you decided actually to turn towards Dublin,
that is a 45 minute routing,
so you definitely have another 10 minutes where you're gonna burn some extra fuel,
meaning that you're definitely gonna be below your max landing weight.
But, another important fact is to mention that the dumping operations have to be coordinated with air traffic control,
so ATC can take precautions to keep other aircraft clear of such areas.
And, if applicable, the procedure is usually accomplished at high altitudes where the fuel will dissipate before reaching the ground.
So, once you've reached a landing weight below the maximum weight, you set up for approach and perform a normal landing.
Smaller jet airliners, like a Boeing 737 or the Airbus A320,
which aren't fitted with the fuel jettison system, have to burn the fuel by flying
holding patterns until the airplane weight is below the maximum landing weight, or in urgent cases, perform a
overweight landing procedure, but that's a whole other video right there.
And there's one more procedure, which the Royal Australian Air Force used during the closing ceremony of the Summer Olympics in 2000,
with their F-111 Aardvark fighter jets: the "dump and burn," only to get a great show!
They sure handle things differently in the land down under.
I hope you enjoyed this basic introduction video about the fuel dumping procedure.
Make sure to perform a touch and go up at my Instagram account.
Make sure you not over your maximum landing weight, and hit the subscribe button plus the notification bell
so you won't miss out upcoming videos.
Thank you much for your time, wishing you all the best, your Captain Joe.
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